Wu Yuping, Wang Tao
State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
J Colloid Interface Sci. 2015 Jun 15;448:100-5. doi: 10.1016/j.jcis.2015.02.020. Epub 2015 Feb 13.
It was found that the procedures for incorporating hydrated salts into silica, including mixing with sol in an instant (S1 procedure), mixing with sol via drop by drop (S2 procedure) and mixing until the sol forming the gel (S3 procedure), had pronounced effects on the phase change enthalpy of hydrated salts/silica composite via sol-gel process. The discrepancy of phase change enthalpies of the composites with the same content of hydrated salts can be as high as 40 kJ/kg. To unveil the mechanism behind, the pore structure of silica matrix and interfacial functional groups were investigated extensively. It was revealed that different incorporation procedures resulted in distinct pore structure of silica matrix and different intensities of interfacial Si-OH groups. The S3 procedure was beneficial to induce the silica matrix with bigger pore size and fewer Si-OH groups. Consequently, the phase change enthalpy of the hydrated salts/silica composite prepared by this procedure was the highest because of its lower size confinement effects and weaker adsorption by Si-OH groups. This study will provide insight into the preparation of shape-stabilized phase change materials for thermal energy storage applications.
研究发现，将水合盐掺入二氧化硅的过程，包括瞬间与溶胶混合（S1法）、逐滴与溶胶混合（S2法）以及混合直至溶胶形成凝胶（S3法），对通过溶胶-凝胶法制备的水合盐/二氧化硅复合材料的相变焓有显著影响。相同水合盐含量的复合材料的相变焓差异可高达40 kJ/kg。为揭示其背后的机制，对二氧化硅基质的孔结构和界面官能团进行了广泛研究。结果表明，不同的掺入过程导致二氧化硅基质具有不同的孔结构和不同强度的界面Si-OH基团。S3法有利于诱导形成孔径较大且Si-OH基团较少的二氧化硅基质。因此，通过该方法制备的水合盐/二氧化硅复合材料的相变焓最高，这是因为其尺寸限制效应较低且被Si-OH基团的吸附较弱。本研究将为用于热能存储应用的形状稳定相变材料的制备提供见解。
